Intra-aortic heart pump



April 14, 1970 M. s. HEILMAN INTRA-AORTIC HEART PUMP Z5 Sheets-Sheet 1Filed March 1'7, 1967 v/P I l I A INVENTOR MARL/N 5. HE/LMAN ZiZzZZmWATTORNEYS A ril 14, 1970 M. s. HElLMAN 3,505,937

INTRA-AORTIG- HEART PUMP Filed March 1'7, 1967 3 Sheets-Sheet 2 MARLIN5. HE/LMA/V ATTORNEYS R WAVE April 14, 1970 M. s. HEILMAN INTRA-AORTICHEART PUMP s Sheets-Sheet 5 Filed March 17, 1967 M 11 L? m M] VF. w NH 23 9 I P02 8 n w 02 l e H 2W3 W C mo... m 02 E fi m n A .L l 0? M no.2005 m x m m -m 8 w o m p o E -0 L 6 m S I 6 w. m T a m J 4 Am F T M -mw a E L M o D m m 0 W M m w W M O O l 3 4 D uK 355 mm m umammwmm cm FaBide ATTORNEYS United States Patent 3,505,987 INTRA-AORTIC HEART PUMPMarlin S. Heilman, Gibsonia, Pa., assignor to Medrad,

Incorporated, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar.17, 1967, Ser. No. 624,082 Int. Cl. A61]: 19/00 US. Cl. 128-1 35 ClaimsABSTRACT OF THE DISCLOSURE A counterpulsation system for aiding coronarycirculation wherein an expansible impeller means is located within theaorta of a patient. Pressure regulating means are provided for expandingand contracting said impeller while simultaneously reciprocating itWithin the aorta, the motion of said impeller being synchronized withthe pumping activity of the heart by means of a variable control circuitto reduce aortic pressure during systole and increase it duringdiastole.

BACKGROUND OF THE INVENTION The present invention relates to a methodand apparatus for assisting the flow of blood and maintaining itspressure within the aortic artery of a cardiovascular system. Moreparticularly, it relates to a method and apparatus for carrying out theprinciple of counterpulsation whereby cardiac work is aided by loweringaortic pressure during systolic ejection and by raising the diastolicpressure.

Heart disease is the leading cause of death in the United States today.A large fraction of heart deaths are caused by acute (sudden) partial orcomplete obstructions of blood flow to the heart muscle, causing heartmuscle weakness or abnormal electrical phenomena which, in turn, makethe heart nonfunctional as a pump. Many of these obstructions,hereinafter called coronary occlusions, result in death within hours ordays of their occurrence. It is probable that, if the heart wereassisted during the first critical hours, the reparative andregenerative powers which are inherent in the heart could preserve lifein a large number of victims of such attacks.

During normal functioning of the heart, one complete heart cycle takesapproximately one second and consists of two time intervals. The firstinterval is termed systole (approximately 300 milliseconds), duringwhich the arotic valve is open and the left ventricle contracts andsqueezes blood into the aorta. At this time, the pressure within theleft ventricle is in equilibrium with the aortic pressure. The secondinterval (approximately 700 milliseconds) is termed diastole, and isthat time following systole during which the aortic valve is closed andthe left ventricle is being filled through the mitral valve. The aortais a large extendible elastic tube that dampens the pulsatile characterof the blood being ejected from the heart and provides a conduit for thehigh pressure arterial blood to move into the various organs of thebody. Immediately above the aortic valve are located the openings of thecoronary arteries which supply arterial blood to the heart, itself. Itis during diastole that the greatest amount of coronary flow takesplace. Not only is the time interval longer, but the intra-muscularpressure is lower since less work is involved during this period, thusallowing more blood to pass through the coronary system.

Upon the occurrence of an acute occlusion of one of the principalcoronary arteries, with consequent oxygen and nutrient starvation of therespectively supplied heart muscles, the left ventricle becomes weakenedand, depending on various compensatory physiological mechanisms, isoften unable to eject sufiicient blood to maintain 3,505,987 PatentedApr. 14, 1970 a normal aortic pressure. Such an event has a degeneratingelfect on heart viability because the coronary circulation suffersfurther from the lower driving blood pressure head in the aorta.

It has been recognized for a number of years that the effects of thisdegenerating cycle could be offset through the principle ofcounterpulsation. This concept suggests that some means should beemployed to aid systolic ejection by means of lowered aortic pressureand to increase coronary circulation by raising the diastolic pressure.Many techniques for accomplishing counterpulsation have been developed,but these have not been entirely satisfactory in that they are imprecisein their timing, do not affect both the systolic and diastolic portionsof the cycle, or are ineffective. For example, some systems concentrateonly on raising diastolic pressure, but such diastolic augmentationsystems fail to assist in the systolic ejection of blood from the leftventricle. It is, therefore, an object of the present invention toprovide an improved method and apparatus for accomplishingcounterpulsation wherein both systolic and diastolic portions of theheart cycle are affected.

SUMMARY OF THE INVENTION Briefly, the present invention provides areciprocating pump means which can be implanted in the aorta by way of aguide tube which extends from outside the body of the patient to thearea where the pumping action is to be carried out. The pump meansincludes a driving mechanism, a connecting tube, and a pistonlikeimpeller means so arranged that the intra-aortic impeller may be drivento move back and forth within the aorta. The impeller means may be anelastic balloon or bladder that is inflatable through the connectingtube so that its internal gaseous pressure determines its externaldimensions. Control means are provided for the driving mechanism and apressure regulating mechanism so that the external dimensions of theballoon may be i changed in synchronism with the motion of the impeller.The pressure regulating means may be operated at the end of each strokeso that the pump means has one set of dimensions on the downstroke and asecond set of dimensions on the upstroke, or it may be operated tochange the impeller dimensions during its motion. Electrical programmingmeans are provided for the driving mechanism and for the gas pressureregultaing system so that the pressures generated within the aorta bythe motion of the impeller means will follow a predetermined pattern,thus assisting the heart in its functional cycle and assuring a properblood supply to the coronary arteries. Suitable means are provided togenerate an electric command signal representative of the desiredpressure cycle which is to be established by the position and size ofthe impeller means, and a second signal is generated by the drivingmechanism of the pump, this second signal representing the actualposition of the impeller means within the aorta. These two electricsignals are compared and an error signal derived therefrom, the errorsignal being used to establish the position of the impeller means. Bymeans of this feedback and comparing circuitry, the motion of the pumpmeans is caused to follow the predetermined pattern, which pattern maybe varied in accordance with the requirements of the particular patient.

BRIEF DESCRIPTION OF THE DRAWINGS a cardiovascular system, showing thelocation of the intraaortic heart pump of the present invention;

FIG. 2 is a partial cross-sectional view of the impeller means and theassociated catheter device by which it is positioned in the aorta;

FIG. 3 is a diagrammatic illustration of the gas pressure regulatingsystem for the impeller means of the heart P p;

FIG. 4 is a diagrammatic illustration of a suitable drive mechanism forthe pump;

FIG. 5 is a schematic diagram of a control system suit able for use inthe present invention; and

FIG. 6 is a graphical illustration of the functioning of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawings, there is illustrated in diagrammatic form the muscular leftventricle 10 of a heart which, upon contraction, ejects blood throughthe aortic valve 12 into the aorta 14. Immediately above the aorticvalve are located the openings 16 and 18 leading to the coronaryarteries 20 and 22, respectively. As has been noted, the coronaryarteries supply blood to the muscles of the heart itself, and it is thepartial or complete blockage of blood flow through these arteries andothers (not shown) which is known as a coronary occlusion.

In accordance with the present invention, the blood pressure cycle inthe aorta is maintained at a predetermined cyclical level by means of anintra-aortic device, indicated generally at 24, which is located withinthe longitudinal portion 26 of the thoracic and abdominal aorta. Asillustrated in greater detail in FIG. 2, the intraaortic device 24 iscomprised of an impeller means 30 secured to a connecting tube 32located within, and guided by, a coaxial tube 34. Taken together, theconnecting tube 32 and the guide tube 34 form a catheter device which isdesigned for insertion into the body of the patient, with a portionextending outside the body for connection to a suitableelectro-mechanical actuator, to be described. This actuator permits theimpeller means 30 to be driven back and forth within the aorta by meansof the connecting tube 32 to elfect the desired pressure cycle withinthe aorta. Impeller means 30 acts as an inflatable piston, or balloon,within the aorta, being expansible and contractable in accordance with apressure regulating means connected to it byway of the connecting tube32. An increase in the pressure applied by way of tube 32 to theimpeller causes an increase in its external dimension, the externaldimensions being proportional to and thus controllable by the internalgas pressure.

The guide tube 34 of the catheter is made of Teflon to permit easymotion of connecting tube 32 within its central opening. Surrounding theTeflon tube 34 is a fluid or elastic medium, such as liquid silicon or apolyurethane foam, which acts as a shock absorber between the Teflontubing and an outermost enclosing tube 38. This outermost tubing ispreferably a medical grade silicon rubber so that it is compatible withthe blood stream. The external diameter of tubing 38 is sufficientlylarge that, when the connecting tube 32 is moving reciprocally duringoperation, any laterally transmitted force is first dampened by theshock absorbing material 36 and then distributed over a large crosssectional area of aortic wall. The large circumference of the externalsilicon tubing and the shock absorbing material within it thus serve toprevent damage to the walls of the aorta.

Both ends of the external silicon rubber tube 38 are smoothly sealed tothe Teflon guide tube 34, which, in turn, snugly sheaths the connectingtube 32. The proximal end of the catheter device 24, which end extendsout of the aorta of the patient, is attached to the external drivingmechanism in the manner illustrated in FIG. 4. The Teflon guide tube 34and the external sealed silicon tubing 38 are both attached to astationary support 40 on the electro-mechanical actuator, while themovable, semirigid, connecting tube 32 is attached to a movable drivermechanism 42. This arrangement permits the connecting tube to be movedlongitudinally inside the aorta and inside the catheter device. Thecatheter tubing is fastened to the stationary support 40 by any suitablemeans such as threads 44, while the inner connecting tube 32 is attachedto the movable drive means 42 by any suitable means such as threads 46.

The expansible central lumen, or chamber 48 of the intra-aorta impellermeans communicates through the axial opening 50 of connecting tube 32and through a flexible tube 52 with a source of a biologicallyacceptable gas such as carbon dioxide. Such a source is illustrateddiagrammatically in FIG. 3 wherein a carbon dioxide cartridge isattached by means of a threaded connection '62 to a gas line 64. Line 64includes a manually controlled needle valve 66 which is followed by apreset pressure relief valve 68. The pressure relief valve 68 isincluded to prevent explosion of the intra-aortic impeller shouldexcessive pressure from the CO cartridge 60 flow into the system. Line64 includes a miniature accumulator 70 having a flexible wall 72 whichis movable by means of a solenoid 74. The movable wall, or diaphragm, isin the form of a plastic bag, and is preferably of a vinyl materialwhereby motion of the piston may vary the volume of accumulator 70. Thesolenoid is operated by means of a variable direct current source 76connected to the coil of the solenoid through an on-off switch 78.Currrent source 76 may be manually variable or it may be automaticallyvaried in accordance :with a predetermined program. Switch 78 may bemechanically operated or may be an electronic device such as atransistor switch; in either event, it must be of a suitable type torespond to the control signals provided by the programmed controller ofFIG. 5, to be described.

A pressure gauge 80 is provided in gas line 64 downstream fromaccumulator 70 to monitor the pressure being applied to the centrallumen of impeller 30 by way of flexible tube 52. The initial pressureand volume, hereinafter termed P V of the impeller is determined withswitch 78 opened. The system is filled with carbon dioxide throughneedle valve 66 until pressure P is reached, as determined by pressuregauge 80. The needle valve is then closed and the pressure regulatorsystem is ready for operation. When switch 78 is closed, solenoid 74produces a piston action on diaphragm 72 in accordance with themagnitude of the current supplied by source 76. This piston actionincreases the pressure in the system, which increase is registered onpressure gauge 80 as P pressure P being proportional to the current fromsource 76. At pressure P the impeller means 30 will expand to a secondvolume V and will take on a correspondingly increased externaldimension. Thus, the impeller may be a bi-stable pressure-controlleddevice which will have two sets of dimensions depending upon Whether itis subjected to pressures P or P and depending on its particular shapeand expansion characteristics. If a programmed variable current source76 is used, multiple pressure and volume states may be created in thesystem during each cycle of the heart pump operation, thus permitting afurther control over the pressure pattern within the aorta. Thedesirability and extent of such-additional variations would depend onthe particular patient being treated.

Referring now to FIG. 4, there is illustrated an electromechanicalactuator which is designed to reciprocate the pistonlike impeller means30 within the aorta, the stroke, or distance, and the timing of themotion being controllable in accordance with a predetermined pattern orprogram. The actuator is mounted in a suitable housing or may beattached to a suitable platform 84, and includes the stationaryconnecting element 40 which is adapted to receive the threads 44 of thecatheter device 24. The driver means 42 is fastened to a positive drivetiming belt 86 which passes around a geared drive pulley 88, an idlerpulley 90 and a potentiometer 100. Pulleys 88 and 90 are so located onplatform 84 that the portion of the timing belt 86 which carries driver42 is parallel to the semi-rigid connecting tube 32 extending fromstationary support 40. As has been noted, connecting tube 32 is fastenedto driver 42 by means of suitable threads 46', thus rotation of drivepulley 88 causes drive means 42 to move tube 32 within the catheterdevice 24.

The geared drive pulley 88 is connected to the rotary armature 92 of adirect current, limited rotation torque motor 94. This motor, which maybe a Series TQ18W brushless DC torque motor, manufactured by AeroflexLaboratories, Inc., of Plainview, Long Island, N.Y., is a precisionactuator having an angular motion limited to approximately :60 rotation,with a linear torque output. In operation, the armature of the torquemotor 94 rotates clockwise through approximately two radians in responseto an input signal of one polarity, introducing a linear stroking motionto driver mechanism 42. This motion is transferred through connectingtube 32 to the intraaortic impeller means 30, causing the impeller tomove downwardly in the aorta, as viewed in FIG. 1. The direction andextent of this motion is indicated in FIG. 4 by arrow 96 and in FIG. 1by arrow 96. Upon reversal of the energizing signal to motor 94,armature 92 I0- tates in a counterclockwise direction through the sametwo radians, introducing a reverse linear stroking motion to the drivermechanism 42 and to the impeller 30. This reverse motion is indicated byarrows 98 and 98' in FIGS. 4 and 1, respectively.

The motion of armature 92, and thus of drive mechanism 42 and impeller30, is monitored by means of potentiometer 100 which is supported onplatform 84 and driven by timing belt 86. The setting of potentiometer100 thus represents the position of the impeller within the aorta, andprovides a feedback signal which can be compared with a command signalto adjust the impeller to one or more predetermined positions during thecourse of a timing cycle. This control system is illustrated in FIG. 5,which is seen to consist of circuitry for generating a command signal110, circuitry for providing a feedback position signal 112, and circuitmeans for comparing these two signals to produce a resultant, or error,signal 114. This error signal is amplified by a suitable amplifier 116and is used to drive the motor 94 in a direction corresponding to thesignal polarity, thus causing the motor to follow a desired pattern ofmotion.

Command signal 110 is a generated function which varies in amplitudewith time in conformity with a determinable pattern. Although numeroustypes of signal generators will be suitable for this system, a preferredmethod of generating the desired wave form is set forth herein. Asshown, the command signal is a function generated by multiplepotentiometers and time delay circuits which are sequentially gated toan output line in given time increments. The advantage of this type ofarrangement is that the plurality of potentiometers permit a flexiblebut exact manual setting of the desired amplitude for each step of thecycle, thus permitting generation of a wave form that gives close andaccurate control over the motion of impeller 30, allowing this motion tobe exactly matched to the requirements of each individual patient. Acomplete cycle of the command signal 110 is generated in response to asingle output from a Schmitt trigger 120. The Schmitt trigger producesan output pulse on line 122 in response to the standard R wave of anelectrocardiogram, which wave is illustrated at curve B in FIG. 6. Theoutput signal on line 122 may be applied through line 124 to the switchmeans 78 (FIG. 3) to open this switch and thus to insure that 1 Vconditions of pressure and volume exist in the impeller 30. In addition,the signal on line 122 activates a clock means,

such as an oscillator 126, which produces a pulse every 0 the first timedelay. The step motor tacts P through P tacts preceding contact P 40through line 172 to oscillator 6 25 milliseconds. These clock pulses areapplied through line 128 to a time delay circuit 130 which is preset tothe desired value and, typically, might provide a delay of 100milliseconds, or 4 clock pulses.

At the end of the time delay, a gating means is activated to connectsuccessive potentiometers to an output line to produce the desiredcommand function. The gating means shown here, for purposes ofillustration, is comprised of a step motor 132 which receives fromoscillator 126 stepping pulses through line 134 at the end of advances amovable arm 136 to successive contacts P through P of cora respondingpotentiometers which are so connected in the command circuit as toprovide the desired wave form and control. As an example, at the end ofthe delay provided by delay circuit 130, movable arm 136 is connectedsuccessively to contacts P through P thus connecting 6 differentpotentiometers 140 through between a regulated source of negativevoltage 146 and out- 20 put line 148, each step producing on line 148 adistinctive voltage level determined by the setting of the correspondingpotentiometers. When arm 136 reaches contact P a second time delay isinitiated, during whicr time switch 78 in FIG. 3 is closed to change thepres sure and volume conditions in the impeller means 30 t( P v as hasbeen described. This may be effected con veniently by connecting aconductor 150 between contac P and the actuator means for switch 78,whereby th negative voltage on arm 136 is applied to such actuatin 30means. It will be apparent that the output from any on of the contactsmay be used for this purpose, dependin upon the timing desired foroperation of switch 78.

The time delay at this point in the cycle is obtaine simply by causingarm 136 to be gated to a series of C0] which are not connected to outpiline 148. It will be apparent that any desired time delz means may beused here. Similarly, it will be appare that the time delay provided bynetwork 130 may al: be provided by a corresponding use of unconnected coto which arm 136 could l gated by step motor 132. Upon connection of arm136 contact P and until its connection with contact P the signal on line148 is varied by means of potentio. eters 151 through 170. When arm 136reaches cont: P the negative voltage carried by arm 136 is appli 126,cutting off the oscil tor denergizing step motor 132. This ends thecycle operation of the control network and it remains quiesc untilactivated by a succeeding R wave from the elect cardiogram of thepatient.

The steps between the various voltage levels of command signal 110 maybe smoothed out by me of a suitable filter network, such as that formedby pacitor 174 and resistor 176, before being compared v feedback signal112. The filter network may also se to maintain the voltage on line 148at the level set potentiometer 145 during the time delay caused by ctacts P through P if desired.

The feedback signal from potentiometer 100 is der by means of movablearm 178, the arm being conne through resistor to the input line 182 ofamplifier where the signals 110 and 112 are compared. Mov arm 178 isdriven by means of motor 94 through medium of timing belt 86 in themanner described at 6 The error signal 114 appearing on line 182 iseither 1 tive or negative, depending upon whether the electri positiveosition signal derived from potentiometer has a magnitude that isgreater or lesser than that o electrically negative command signal 110.The outpu 7 nal from amplifier 116 appearing on line 184 is an a1 fiedversion of the input error signal 114, and is ap to the stator of motor94 in such a manner as to r the armature to move in a direction toreduce the signal to zero, in the known manner.

Referring now to the graph of FIG. 6, curve A trates a typical commandfunction which may be generated by the gated potentiometers of FIG. 5.It will be noted that the voltage produced by the successivepotentiometers varies between and volts, depending upon the setting ofthe particular potentiometers. As shown in this example, the successivecommand voltages during systole decrease in value, causing the armatureof motor 94 to rotate in a clockwise direction to move impeller means 30downwardly in the aorta, as illustrated in curve E, until the desireddisplacement has been achieved. At this time, the second time delay isinitiated, and the shift of the pressure state in the impeller to P V,is begun. Upon completion of the second time delay, the command functionbegins to drive the motor armature in a counterclockwise direction,moving the impeller upwardly in the aorta at a rate determined by thechange in amplitude of the command function. The upward motion ofimpeller 30 is seen from curve E of FIG. 6 to occur during diastole,with the piston means expanded to the diameter governed by the P V,condition. Upon completion of the cycle at contact P the system restsuntil again triggered to cycle.

The displacement distance of the intra-aortic device is measured bypotentiometer 35, whose output constitutes curve C in FIG, 6. It will beseen that curve C follows the shape of command function A, althoughreversed in polarity, thus illustrating the manner in which the systemfollows the command function. In this manner the electromechanicalactuator gives a controlled and predictable position, velocity andacceleration behaviour pattern to the intra-aortic device. This devicecycles up and down within the aorta a constant distance, but itshemo-dynamic efiect differs during the two parts of the cycle throughvariations in its external dimensions. These changes in dimension withdisplacement are illustrated in curve E.

The curves and areas shown in section D of FIG. 6 correspond to thepressure vs. time values that exist in the aortic root 14 (FIG. 1),during the two phases of the heart cycle, that is, during diastole andsystole, Curve 190 illustrates an abnormally low aortic root pressuresuch as might exist in a failing heart. Curve 192 represents a newintra-aortic pressure curve that would be produced by successfulcounterpulsation wherein the systolic pressure is reduced and thediastolic pressure is increased. It will be noted that, during systole,there is a time-pressure integral 194 which represents the lowerpressure force which the left ventricle opposes when its outlet valve 12is open with the use of the present invention. Time-pressure integral196, which is the area between curves 190 and 192 during diastole,represents the increased intra-aortic pressure which is availablethrough use of the invention to drive blood into the coronary arteries20 and 22 (FIG. 1) to overcome the effects of a coronary occlusion. Byproper programming of the present system, a time-pressure integral of apressure spike nature, such as that illustrated at 198, may be provided.Such a pressure spike can be useful in stimulating certaincardiovascular reflexes.

Although particular apparatus for carrying out the present invention hasbeen set forth herein, it will be apparent to those skilled in the artthat numerous variations may be made without departing from the spiritof the invention, Thus, for example, in place of potentiometer 100, atachometer or accelerometer could be used with appropriate electricalcircuitry to provide equivalent feedback displacement vs. timeinformation. In place of the pinrality of individually adjustablepotentiometers, the command function could be automatically generated bya variety of known circuits. In addition, in certain circumstances, itmay be desirable to replace the illustrated pressure-volume regulatorwith a second pistonlike member surrounding the impeller means 30,whereby variations in the external dimensions and consequenthemo-dynamic effect of the second member would be produced through thestroking action of piston means 30 therewithin.

It will be appreciated that the principles and apparatus be adapted foruse in influencing the flow of fluid in any body canal, and that suchflow can be programmed to follow any desired pattern, although theprincipal purpose for which the present device is adapted is its use inassisting an acutely failing heart until the hearts own regenerativepowers can eliminate the need for such an assist. Normally, theintra-aortic device of this invention would be inserted to a positionrelatively close to the aortic root so that the maximum effect of itsoperation would appear in the coronary arteries, but there may becircumstances where it would be located elsewhere. Thus, variousomissions and substitutions in the device and method illustrated anddescribed may be made without departing from the spirit of theinvention.

I claim:

1. Pump means for modifying fluid flow within a human or animal body,comprising: impeller means adapted for location within a fluid flowpassage; driver means for moving said impeller within said passage;control means for operating said driver means in accordance with adeterminable pattern; and means for varying the dimensions of saidimpeller by expanding and contracting said impeller in conformity withsaid pattern.

2. The pump means of claim 1, wherein said driver means includesconnecting means for attaching said impeller means to said driver means,said driver means being operable to impart reciprocal motion to saidconnecting means and said impeller means within said flow passage.

3. The pump means of claim 2, further including guide means for saidconnecting means, said guide means comprising a relatively stationarycatheter consisting of an innermost low friction tube, intermediateshock absorbing means, and an outermost sealing tube, whereby saidconnecting means can move freely within said innermost tube to transmitmotion from said driver means to said impeller means.

4. The pump means of claim 1, wherein said impeller means comprises ahollow, elastic member having a central lumen; wherein said means forvarying the dimensions of said impeller comprises a source ofpressurized gas connected to said lumen; and wherein said driver meansincludes mechanical actuator means connected to said lumen.

5. The pump means of claim 1, wherein said variable control meansincludes means for producing a command signal; means for generating afeedback signal corresponding to the position of said impeller in saidpassage; and means for comparing said command and feedback signals.

6. The pump means of claim 5, wherein said command signal is anelectrical signal having a Waveform shaped in accordance with saidpattern and said feedback signal is an electrical signal having awaveform determined by the motion of said impeller.

7. The pump means of claim 2, wherein said driver means comprises anelectro-mechanical actuator having a reversible DC torque motor and apositive drive timing belt connected between said motor and saidconnecting means.

8. A counterpulsation pump for aiding blood circulation, comprising:impeller means adapted for location within a cardiovascular system;drive means for longitudinally displacing said impeller means withinsaid system; and control means including means responsive to theposition of said impeller for moving said impeller drive means inconformity with a determinable pattern.

9. The counterpulsation pump of claim 8, wherein said drive meanscomprises mechanical actuator means and connector means attaching saidimpeller means to a movable portion of said actuator means; said controlmean: regulating the motion of said actuator means whereby sair impelleris moved in conformity with said determinabli pattern.

10. The counterpulsation pump of claim 8, whereii said control means isvariable to establish said pattern.

described herein may 11. The counterpulsation pump of claim 8, whereinsaid drive means includes semi-rigid connector means between said drivemeans and said impeller means, whereby said impeller and said connectorare moved longitudinally within said system by said drive means.

12. The counterpulsation pump of claim 8, wherein said drive means isreversible; said control means determining the direction, magnitude andvelocity of motion of said drive means to move said impeller meansaccordingly.

13. The counterpulsation pump of claim 12, wherein said control meanscomprises means for generating a command signal, means for deriving afeedback signal corresponding to the position of said impeller meanswithin said system, means for comparing said command and feedbacksignals to produce a resultant signal, and means for operating saiddrive means in accordance with said resultant signal.

'14. The counterpulsation pump of claim 13, wherein said means forgenerating a command signal is variable, whereby any arbitrary patternmay be established.

15. The counterpulsation pump of claim 14, wherein said command signalis an electrical signal having a waveform corresponding to the bloodpressure variations to be established in said cardiovascular system.

16. The counterpulsation pump of claim 14, wherein said command signalis an electrical waveform having a magnitude and polarity which isvariable to produce a displacement in said impeller means which servesto reduce the pressure of blood in said cardiovascular system duringsystole, and which serves to increase said pressure during diastole.

17. The counterpulsation pump of claim 13, wherein said feedback signalis an electrical signal having a waveform corresponding to the motion ofsaid impeller means.

18. The counterpulsation pump of claim 13, wherein said control meansfurther includes means for varying the dimensions of said impeller meansduring the motion of said impeller means within said system.

19. The counterpulsation pump of claim 18, wherein said impeller meansconsists of a hollow, elastic piston-like member having a central lumen,said means for varying the dimensions of said impeller means including asource of pressurized gas, tube means connecting said source of gas withsaid central lumen, and means for regulating the pressure of said gas,whereby the size of said impeller corresponds to the pressure of the gaswithin said central lumen.

20. The counterpulsation pump of claim 18, wherein said drive means fordisplacing said impeller means comprises electro-mechanical actuatormeans external of said cardiovascular system; semi-grid connector meansattaching said impeller means to a movable portion of said actuatormeans; and catheter means adapted to extend from a stationary portion ofsaid actuator means into said cardiovascular system to guide saidconnector means.

21. The counterpulsation pump of claim 20, wherein said impeller meansconsists of a hollow, elastic, pistonlike member having a central lumen,said semi-rigid connector means comprising a tube having a passagecommunicating with said central lumen, whereby gas under pressure may befed to said central lumen to inflate said impeller means.

22. The counterpulsation pump of claim 20, wherein the movable portionof said electro-Inechanical actuator means includes a reversible motor,having limited rotation, said motor being attached to said semi-rigidconnector means for reciprocably driving said impeller means.

23. The counterpulsation pump of claim 22, wherein said means forderiving a feedback signal comprises ptentiometer means having a movablearm driven by said reversible motor, whereby the position of said armcorresponds to the location of said impeller means.

24. The counterpulsation pump of claim 20, wherein said catheter meanscomprises an innermost low friction tube, intermediate shock absorbingmeans, and an outermost sealing tube, whereby said connector means canmove freely within said innermost tube to transmit motion from saiddrive means to said impeller means without damage to said cardiovascularsystem.

25. The counterpulsation pump of claim 13, wherein said means forgenerating a command signal includes an input line, an output line, aplurality of potentiometers, and gating means for connecting successivepotentiometers between said input and output lines, said output lineconnecting said command signal to said means for comparing.

26. The counterpulsation pump of claim 25, wherein said gating meansincludes means for generating clock pulses; step motor means responsiveto said clock pulses to connect said potentiometers; and means forinitiating and means for terminating the generation of said clockpulses.

27. The method of effecting counterpulsation in a cardiovascular system,comprising:

(a) inserting a reciprocable impeller means within the aortic artery ofsaid system;

(b) deriving a first electric signal corresponding to a predeterminedpoint in the diastole-systole cycle of said system;

(c) generating in response to said first electric signal a second,varying electric signal corresponding to a predetermined intra-aorticpressure cycle;

(d) generating a third, varying electrical signal corresponding to theposition of said impeller means within said system;

(e) comparing said second and third signals to produce an error signal;

(f) and moving said impeller means in a direction to reduce said errorsignal, whereby the motion of said impeller means is in conformity withsaid predetermined intra-aortic pressure cycle.

28. The method of claim 27, further including the step of expanding andcontracting said impeller means in timed relationship to thereciprocating motion of said impeller means.

29. The counterpulsation pump of claim 8, wherein said impeller meansconsists of a hollow, elastic pistonlike member having a central lumen,said drive means for longitudinally displacing said impeller meanscomprising a semi-rigid connector, said pump further including cathetermeans adapted to extend into said cardiovascular system to guide saidconnector means.

30. The counterpulsation pump of claim 29, wherein said catheter meanscomprises an innermost low friction tube, intermediate shock absorbingmeans, and an outermost sealing tube, whereby said connector means canmove freely within said innermost tube to transmit motion from saiddrive means to said impeller means without damage to said cardiovascularsystem.

31. The counterpulsation pump of claim 30, wherein said semi-rigidconnector means has a passage communicating with said central lumen,whereby gas under pressure may be fed to said central lumen to vary thedimensions of said impeller means.

32. An intra-aortic pump for counterpulsation of a heart, comprising ahollow, elastic, pistonlike impeller having a central lumen, a drivemeans for longitudinally displacing said impeller, semi-rigid connectormeans attaching said impeller to said drive means, and catheter meansadapted to extend into a cardiovascular system to guide said connectormeans.

33. The pump of claim 32, wherein said connector means includes apassage communicating with said lumen, said pump further including asource of pressurized gas and means for regulating the pressure of saidgas, whereby the dimensions of said impeller may be varied.

34. The pump of claim 32, wherein said catheter means comprises aninnermost low function tube, intermediate 1 1 shock absorbing means, andan outermost scaling tube, whereby said connector means can be movedfreely within said innermost tube for longitudinal displacement of saidimpeller to reduce systolic pressure and to increase diastolic pressure,said shock absorbing means serving to prevent damage to saidcardiovascular system due to the motion of said connector means.

35. The pump of claim 34, wherein said drive means comprises anelectro-mechanical actuator adapted to reciprocate said impeller, saidpump further including means for varying the external dimensions of saidimpeller in synchronism with the longitudinal displacement of saidimpeller.

References Cite UNITED STATES PATENTS 3,266,487 8/1966 Watkins et al128-1 3,352,303 11/1967 Delaney 128-24 OTHER REFERENCES Callaghan etal., Transactions, June 19, 1965, pp. 36-39.

10 L. W. TRAPP, Primary Examiner US. Cl. X.R.

